Maximum size of a Thread MESH network

[Di Piazza Alain]

When we look to the spec, we can see that inside the RLOC there are 5 bits used to define the Router ID and 9 bits to define the child ID.

It the spec it means that there are  a maximum of 32 routers and as specified in the spec, the Child ID can be in the range of 1 through 511.

Question 1 : Does it mean that in theory, we could have a Thread mesh network with 32 x 511 devices connected ??
Question 2 : In the literature, we often see a limit of 250 maximum devices connected. How is computed this value ?
Question 3 : Inside OpenThread, we can configure OPENTHREAD_CONFIG_MAX_CHILDREN which is by default 10. What is the maximum value of this define ?

Question 4 : What are the more relevant parameters inside OpenThread which we can tune in order to size the mesh network (apart from OPENTHREAD_CONFIG_MAX_CHILDREN )

Question 5 : On GRL there are tests with 32 nodes, but do you know what is the biggest Thread mesh network that has been tested so far, on which platform and with which topology ?

Thanks very much for your answers,

Alain Di Piazza

[Jonathan Hui]

See below:

On Fri, Sep 22, 2017 at 2:31 AM, Di Piazza Alain <dipiaz...@gmail.com> wrote:

When we look to the spec, we can see that inside the RLOC there are 5 bits used to define the Router ID and 9 bits to define the child ID.

Router ID is 6 bits.  Child ID is 9 bits.

There is a maximum of 32 active routers, but the larger namespace avoids reusing deprecated router IDs for some time.

It the spec it means that there are  a maximum of 32 routers and as specified in the spec, the Child ID can be in the range of 1 through 511.

Question 1 : Does it mean that in theory, we could have a Thread mesh network with 32 x 511 devices connected ??

Yes.

 

Question 2 : In the literature, we often see a limit of 250 maximum devices connected. How is computed this value ?

Routers are not required to support 511 devices.  The current Thread Conformance document specifies a minimum of 10.

 

Question 3 : Inside OpenThread, we can configure OPENTHREAD_CONFIG_MAX_CHILDREN which is by default 10. What is the maximum value of this define ?

The current maximum is 64.  However, we can increase this further with some minor changes.

 

Question 4 : What are the more relevant parameters inside OpenThread which we can tune in order to size the mesh network (apart from OPENTHREAD_CONFIG_MAX_CHILDREN )

Some other configurations to consider:

- OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS: to handle additional traffic

- OPENTHREAD_CONFIG_ADDRESS_CACHE_ENTRIES: to handle additional destinations

- OPENTHREAD_CONFIG_COAP_SERVER_MAX_CACHED_RESPONSES: to handle more CoAP interactions

 

Question 5 : On GRL there are tests with 32 nodes, but do you know what is the biggest Thread mesh network that has been tested so far, on which platform and with which topology ?

SiLabs published an app note about a test network of 217 nodes.

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Jonathan Hui